Strainer and an associated pumping method

ABSTRACT

As shown for example in FIG.  5 , the strainer  13  has a body  2  that defines a plurality of inlet holes  3  each having a perimeter that is extensible by at least 20%. Each of the inlet holes  3  is in fluid communication with a hollow internal chamber. In use, liquid is sucked through the holes  3 , thereby straining out larger contaminants such as rocks and stones, into the hollow internal chamber and then out the outlet. The majority of the strainer  13  is formed from a resilient deformable material that allows opposed sides of the internal chamber to be brought into contact with each other in response to the application of a compressive force. Once the force is no longer being applied, the resilience of the material allows the body  2  to resiliently return to substantially its pre-deformation shape.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of pending U.S. patent applicationSer. No. 15/561,020, filed Sep. 22, 2017, entitled “A Strainer and anAssociated Pumping Method”, which claims the benefit of PCT ApplicationNumber AU2016/050160, filed Mar. 8, 2016, which claims the benefit ofAustralian Patent Application Number 2015901050, filed Mar. 24, 2015 andAustralian Patent Application Number 2015902356, filed Jun. 19, 2015.The aforementioned applications are hereby incorporated herein byreference.

TECHNICAL FIELD

The present invention relates to a strainer that may be attached to theend of a hose into which liquid is to be pumped and an associatedpumping method. Embodiments of the present invention find application,though not exclusively, in contexts such as mining and firefighting.

BACKGROUND ART

Any discussion of documents, acts, materials, devices, articles or thelike which has been included in this specification is solely for thepurpose of providing a context for the present invention. It is not tobe taken as an admission that any or all of these matters form part ofthe prior art base or were common general knowledge in the fieldrelevant to the present invention as it existed in Australia orelsewhere before the priority date of this application.

It is known to attach a strainer to the inlet of a hose when attemptingto pump liquids such as water, which may be muddy and may also becontaminated with foreign objects such as rocks and stones, etc. The endof the hose to which the strainer is attached is immersed within theliquid that is to be pumped. The purpose of the strainer is to strainout larger contaminants so that the water that is sucked by the pumpinto the hose only contains contaminants that are small enough to passthrough the strainer.

The inventors of the present application have appreciated that prior artstrainers typically suffer from a number of disadvantages such asdifficulties associated with the unclogging of contaminants and avulnerability to crushing or breakage. The latter of these issues isparticularly prevalent in a mining contexts, such as coal mining by wayof non-limiting example, in which there is an appreciable risk of thestrainer being run over and crushed by heavy machinery.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome, or substantiallyameliorate, one or more of the disadvantages of the prior art, or toprovide a useful alternative.

In one aspect of the present invention there is provided a strainer forattachment to an inlet of a hose, the strainer including: a bodydefining a plurality of inlet holes, each of the inlet holes being influid communication with a hollow internal chamber; and an outlet beingin fluid communication with the hollow internal chamber, the outletbeing to attach to the inlet of the hose; wherein the body is formedfrom a resilient deformable material configured to bring opposed sidesof the internal chamber into contact with each other in response toapplication of a compressive force prior to the body resilientlyreturning substantially to its pre-deformation shape when thecompressive force is no longer applied; and wherein each of the holesdefines a perimeter and wherein each of the holes is extensible so as toextend the perimeter by at least 20%.

In one embodiment the resilient deformable material is, or includes, anelastomeric polymer. In another embodiment the resilient deformablematerial is, or includes, a rubber, synthetic rubber or rubber-likematerial. In yet another embodiment the resilient deformable materialis, or includes, polychloroprene. In yet another embodiment theresilient deformable material is, or includes, nitrile.

According to another aspect of the present invention there is provided amethod of pumping a liquid including: providing a pump attached to ahose, the hose having a distal end defining an inlet; providing astrainer including: a body defining a plurality of inlet holes, each ofthe inlet holes being in fluid communication with a hollow internalchamber; and an outlet being in fluid communication with the hollowinternal chamber, the outlet being for attachment to the inlet of thehose; wherein the body is formed from a resilient deformable material tobring opposed sides of the internal chamber into contact with each otherin response to the application of a compressive force prior to the bodyresiliently returning substantially to its pre-deformation shape whenthe force is no longer applied and wherein each of the holes defines aperimeter and wherein each of the holes is extensible so as to extendthe perimeter by at least 20%; attaching the outlet of the strainer tothe inlet of the hose; operating the pump to suck the liquid into theplurality of holes, through the hollow chamber, out the outlet, and intothe hose; and periodically detaching the strainer and impacting thestrainer against a solid object to dislodge contaminants clogging theholes.

Preferably the method includes periodically reversing the flow directionof the pump such that liquid is pumped out of the holes so as todislodge contaminants clogging the holes.

The features and advantages of the present invention will become furtherapparent from the following detailed description of embodiments,provided by way of example only, together with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

FIG. 1 is a plan view of a first embodiment of the strainer;

FIG. 2 is a cross sectional view of the first embodiment of thestrainer, with the cross section taken through line A-A of FIG. 1;

FIG. 3 is a cross sectional view of the first embodiment of thestrainer, with the cross section taken through line B-B of FIG. 1;

FIG. 4 is a perspective view of a second embodiment of the strainer;

FIG. 5 is a plan view of the second embodiment of the strainer;

FIG. 6 is a plan view of the second embodiment of the strainer showingsome hidden detail;

FIG. 7 is a cross sectional plan view of the second embodiment, with thecross section being taken through line 7-7 of FIG. 5;

FIG. 8 is a rear view depicting the proximal end of the secondembodiment;

FIG. 9 is a front view depicting the distal end of the secondembodiment; and

FIG. 10 is a front view of the second embodiment showing some hiddendetail comprising the positions of the holes 3.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

With reference to FIGS. 1 to 3, the first embodiment of the strainer 1has a body 2 that defines a plurality of inlet holes 3. Each of theinlet holes 3 is in fluid communication with a hollow internal chamber4. The circular outlet 5 of the strainer is in fluid communication withthe hollow internal chamber 4. In use, the strainer 1 is immersed withina liquid that is desired to be pumped. Suction is then provided by apump (not illustrated) so as to suck the liquid through the plurality ofholes 3, thereby straining out larger contaminants, such as rocks andstones. The liquid flows through the holes 3, into the hollow internalchamber 4 and then out the outlet 5.

In use, the outlet 5 is typically attached to the inlet of the hose (notillustrated) that is connected to the pump. A coupling component, in theform of metal ring 7 that is made from 304-316 stainless steel, isembedded within the material that forms the outlet 5 and the remainderof the strainer 1. Connection of the strainer's outlet 5 to the hose isachieved via a hose coupling device (not illustrated), which defines aboss that is shaped to receive the outlet 5 of the strainer 1. A pair ofcams are disposed on opposite sides of the boss such that, once theoutlet 5 of the strainer 1 has been inserted into the boss, the cams arerotated so as to impinge into a groove 6 that extends circumferentiallyaround the strainer 1 immediately adjacent to the embedded metal ring 7.The impinging cams retain the metal ring 7 within the boss, therebyconnecting the strainer 1 to the hose coupling device. To release thestrainer 1, the cams are rotated in the opposite direction so as toprovide clearance for the outlet 5 and its embedded metal ring 7 to bewithdrawn from the boss. At the opposite end to the boss, the hosecoupling device has a shaft that is sized so as to be inserted into thehose. The shaft includes a plurality of ridges that are shaped so as toresist withdrawal of the hose.

Other embodiments of the invention utilise varying means to connect thestrainer to the hose. For example, in another embodiment (notillustrated) a screw thread is formed adjacent the outlet of thestrainer. This allows the outlet of the strainer to be screwed into acorresponding screw thread that is provided within a boss of a hoseconnection device.

The body 2, and indeed the entire strainer 1 with the exception of themetal ring 7, is formed from a resilient deformable material. Thedeformability of the material is such that opposed sides 8 and 9 of theinternal chamber 4 can be brought into contact with each other inresponse to the application of a compressive force. Once the force is nolonger being applied, the resilience of the material allows the body 2to resiliently return to substantially its pre-deformation shape.

The embodiment has passed a test that involved the application of a 100tonne compressive force. As will be appreciated by those skilled in theart, the application of a 100 tonne compressive force causes the hollowinternal chamber to be crushed substantially flat prior to the bodyresiliently returning substantially to its pre-deformation shape whenthe compressive force is no longer applied. Hence, in use, the strainer1 is capable of surviving the application of the type of substantialcompressive force that may be experienced in a mining context, such asbeing run over by a heavy hauling mining vehicle. This comparesfavourably with the prior art strainers of which the applicant is aware,which would be crushed and rendered unusable by the application of sucha compressive force. This is because the prior art strainers aretypically made from either metal or a hard plastics material.Advantageously, the resilient deformable material of the embodiment hasa Young's modulus of less than a Young's modulus of metal or a Young'smodulus of a hard plastics material.

The reduced risk of damaging the embodiment gives rise to practicalbenefits such as longer service life and reduced labour costs and downtime associated with the repair or replacement of broken strainers.Additionally, the reduced risk of damaging the embodiment reduces therisk that broken parts of the strainer 1 may be sucked into the hose andthen into the pump, which advantageously reduces the risk of damagingthe pump.

In one embodiment the resilient deformable material from which thestrainer 1 is made (with the exception of the metal ring 7) includes anelastomeric polymer such as a rubber, synthetic rubber or rubber-likematerial. More particularly, in one embodiment the material is formedfrom a combination of: standard Malaysian rubber, such as SMR10; anactivator such as zinc oxide and/or stearic acid; an accelerator such asN-cyclohexyl-2-benzothiazole sulphonamide (which is also known by thoseskilled in the art as CBS); a crosslinking agent such as sulphur; aprocessing aid such as Struktol A 60 (which is used to reduceviscosity); process oil such as a paraffinic oil; a wax such as aparaffinic wax; an antioxidant and antiozonant such asN-(1,3-Dimethylbutyl)-N′-phenyl-p-phenylenediamine (which is also knownby those skilled in the art as 6PPD) and/orN-Isopropyl-N′-phenyl-p-phenylenediamine (which is also known by thoseskilled in the art as IPPD and which is used to protect the rubber); andsemi re-enforcing carbon black such as N774 (which is used to increasetensile strength).

In another embodiment the resilient deformable material includespolychloroprene (which is also referred to by those skilled in the artas neoprene). More particularly, in this embodiment the resilientdeformable material is formed from a combination of: polychloroprene; acure system and crosslinking agent such as zinc oxide and/or Ethylenethiourea (which is also known by those skilled in the art as ETU) and/orTetramethylthiuram disulfid (which is also known by those skilled in theart as TMTD); a processing aid such as stearic acid and/or StruktolWB212 (which is used as an emulsion plasticizer dispersing andprocessing additive); a flame retardant such as antimony trioxide and/orchlorinated polyethylene and/or alumina trihydrate and/or zinc borate;an acid acceptor such as magnesium oxide; an antioxidant and antiozonantsuch as N-(1,3-Dimethylbutyl)-N′-phenyl-p-phenylenediamine (which isalso known by those skilled in the art as 6PPD); and semi re-enforcingcarbon black such as N330.

In another embodiment the resilient deformable material is, or includes,nitrile, which is an organic compound that has a functional group.

It will be appreciated that the material must be soft enough to deformin response to compressive forces; however hard enough to resistcollapsing due to the vacuum created by the pump. The resilientdeformable material preferably has a Shore A hardness of between 45 and70 and the embodiment has a Shore A hardness of 55. Additionally, it ispreferable for the material to be UV resistant, petrochemical resistant,heat resistant, fire retardant and to have antistatic properties. Withregard to petrochemical resistance, the natural rubber material hasfairly poor properties. However, the polychloroprene-based material hasgood to excellent petrochemical resistance. Additionally, the materialmay be operated in ambient temperatures ranging from −66° C. to +100° C.

The natural rubber-based material has a tensile strength ofapproximately 19 Mpa and can be extended by up to 450% before breakage.The polychloroprene-based material has a tensile strength ofapproximately 16.9 Mpa and can be extended by up to 375% beforebreaking.

The embodiment of the strainer 1 is formed using an injection mouldingprocess using an ENGEL 150 Tonne Clamp injection moulding machine, whichhas two cavities. The cavities hold dies that are shaped in the negativeform of the strainer 1 and each die includes a central post that formsthe hollow internal chamber 4 of the strainer 1. Prior to injection ofthe material, a metal ring 7 is placed into each of the cavities so asto rest on the central post and the metal rings are retained in positionby clipping onto studs. If using the natural rubber-based material, thenit is heated to 170° C. prior to injection. Alternatively, if thepolychloroprene-based material is being used, then it is heated to apre-injection temperature of 175° C. The heated material is theninjected into each of the cavities to make two of the strainers 1. Ifusing the natural rubber-based material, then 0.976 litres of materialper unit is injected into each cavity. Alternatively, if thepolychloroprene-based material is being used, then 0.965 litres ofmaterial per unit is injected into each cavity.

If desired, it is also possible to add colouring agents to the materialso that the strainer 1 may be made in a selected colour.

The strainer 1 is of a unitary construction, which allows for quickerconnection of the strainer 1 onto the hose as compared to the prior artstrainers of which the applicant is aware. More particularly, the priorart strainer are formed in two parts which must be screwed together whenbeing installed in situ. The embodiment dispenses with the requirementfor the installer to screw two separate parts together, which helpsminimise the labour costs associated with installing and replacing thestrainers.

The combined cross sectional area of the plurality of holes 3 ispreferably between 2 and 14 times the cross sectional area of the outlet5. Such a ratio is desirable to provide the strainer 1 with a suitableresistance against blockage. The first embodiment has a total of 240holes, which are arranged in 10 rows, each having 24 holes. Each of theholes 3 is 5 mm in diameter and therefore has a cross sectional area of19.635 mm². Hence, the total cross sectional area of the plurality ofholes 3 is 4712 mm². At its narrowest (i.e. at a cross section taken inthe middle of the groove 6), the outlet is 38 mm in diameter, whichgives the outlet a cross sectional area of 1134 mm². Hence, in the firstembodiment the total cross sectional areas of the plurality of holes is4.15 times the cross sectional area of the outlet 5.

The light weight of the embodiment is another advantage as compared totypical prior art strainers. The embodiment of the strainer 1 weighsless than 1 kg. More specifically, the weight of the embodiment isapprox. 370 grams; whereas the prior art metal strainers typically weighabout 2.5 kg

The body 2 is in the form of a cylindrical shaft defining a distal end10 and a proximal end 11. A tapered head 12 is disposed at the distalend 10. The outlet 5 is at the proximal end 11. The tapered head 12improves the resistance of strainer 1 against the vacuum created by thepump as compared to the resistance that would be provided by a squaredoff head. That is, the tapered head 12 provides support to maintain thedistal end 10 of the body 5 in a cylindrical configuration despite thevacuum created by the pump. This support also helps the strainer toreturn to its shape quicker after the body 5 has been deformed by acompressive force. Another advantage associated with the tapered head isthat it lessens the risk of the strainer 1 being folded in on itself bythe vacuum created by the pump. Preferably the tapered head defines anincluded angle of between 40° and 70° and in the embodiment this angleis 56°.

As can be seen in the figures, the embodiment does not have any sharpedges. This, in addition to the deformability of the material from whichthe embodiment is predominantly made, helps improve safety for thepersonnel and reduce the risk of damage to the equipment in the workplace in which the strainer 1 is being used.

The method of using the strainer 1 when pumping a liquid typicallyinvolves attaching a proximal end of a hose to a pump, with the distalend of the hose defining an inlet. The outlet 5 of the strainer 1 isattached to the inlet of the hose and then the strainer is immersedwithin the liquid that is to be pumped. The pump is then operated so asto suck the liquid into the plurality of holes 3, through the hollowchamber 4, out the outlet 5 and into the hose. Periodically the flowdirection of the pump is reversed so as to pump an amount of liquid,which is typically between 2 to 10 litres, out of the holes 3 andthereby dislodge any contaminants that may be clogging the holes 3.Alternatively, or additionally, the operator may periodically detach thestrainer 1 and impact it against a solid object so as to dislodge anycontaminants that may be clogging the holes 3. Advantageously, theimpacting of the strainer 1 against a solid object is unlikely to damageeither the strainer 1, or the object, due to the deformability of thematerial from which the strainer 1 is formed.

Each of the holes 3 has a perimeter of 15.7 mm Preferably each of theseperimeters is extensible by at least 20%. As mentioned above, thisdegree of extensibility is easily achieved by the material from whichthe embodiment is made, which has been tested to withstand extension byup to 450% in the case of the natural rubber-based material and up to375% in the case of the polychloroprene-based material. Thedeformability and extensibility of the holes 3 is advantageous becauseit facilitates the methods outlined in the preceding paragraph forunclogging of the holes 3 if they get clogged with contaminants such asstones, etc. That is, the deformability and extensibility of thematerial allows the holes 3 to expand and re-shaped themselves asrequired to help eject the contaminants in response to either a reversalof the direction of flow of the pump or in response to impacting of thestrainer 1 against a solid object. In comparison, the stiffness of theholes in the prior art strainers can render them substantially moredifficult to unclog.

A second embodiment of the strainer 13 is shown in FIGS. 4 to 9.Portions of the second embodiment that are similar to those describedabove in relation to the first embodiment have been labelled with thesame reference numerals as used in FIGS. 1 to 3.

The second embodiment differs in that it is longer than that of thefirst embodiment. In the second embodiment, the length of the strainer13 is 370 mm from the proximal end 11 to the distal end 10 (compared to325 mm in the first embodiment). It will, of course, be appreciated thatother embodiments may have differing dimensions.

Another difference between the first and second embodiments is that eachof the holes 3 of the second embodiment are 8 mm in diameter (comparedto 5 mm in the first embodiment). The second embodiment has a total of230 holes. Hence, the total cross sectional area of the plurality ofholes 3 in the second embodiment is 11,561 mm², which is substantiallygreater than the 4,712 mm² of the first embodiment. This allows thesecond embodiment to have a flow rate of up to 850 litres per minute.The dimensions of the outlet 5 of the second embodiment are identical tothose of the first embodiment. That is, at its narrowest, the outlet 5is 38 mm in diameter, which gives the outlet a cross sectional area of1134 mm². Hence, in the second embodiment the total cross sectional areaof the plurality of holes is 10.2 times the cross sectional area of theoutlet 5. Hence, as compared to the first embodiment, the secondembodiment is less likely to become clogged to such an extent that thetotal flow through the strainer 13 is appreciably reduced.

The other main difference between the first and second embodiments isthat the second embodiment has ten projections 14 spaced equally aroundthe body 2. The projections 14 are respectively positioned between eachof the rows of holes 3. Each of the projections 14 is in the form of arib that extends radially away from the centre of the cylindrical body2. This maintains a clearance gap between the lowermost holes 3 and asurface upon which the strainer 13 is resting. In use, the strainer 13typically rests upon the bottom of a body of water with at least two ofthe ribs 13 making contact with the bottom. Hence, those two ribs holdthe lowermost holes 3 up from the bottom of the body of water. Thishelps to avoid the restriction to the flow through the lowermost holes 3that would otherwise occur if the lowermost holes 3 were allowed to restdirectly against the bottom of the body of water.

Another advantage associated with the ribs 14 is their contribution toincreasing the structural integrity of the strainer 13 and in particularthe ribs 14 provide the strainer 13 with further resistance againstbeing sucked inside-out by the pumping vacuum. Additionally, thepresence of the ribs 14 helps to keep any larger objects that may befloating within the body of water away from the inlet holes 3. That is,the presence of the ribs 14 ensures that only objects that are smallerthan the gap between two adjacent ribs 14 can get close to the holes 3,as shown for example in FIG. 10.

While a number of embodiments have been described, it will beappreciated by persons skilled in the art that numerous variationsand/or modifications may be made to the invention without departing fromthe spirit or scope of the invention as broadly described. The presentembodiments are, therefore, to be considered in all respects asillustrative and not restrictive.

1. A strainer for attachment to an inlet of a hose, the strainerincluding: a body defining a plurality of inlet holes, each of the inletholes being in fluid communication with a hollow internal chamber; andan outlet being in fluid communication with the hollow internal chamber,the outlet being to attach to the inlet of the hose; wherein the body isformed from a resilient deformable material configured to bring opposedsides of the internal chamber into contact with each other in responseto application of a compressive force prior to the body resilientlyreturning substantially to its pre-deformation shape when thecompressive force is no longer applied; and wherein each of the holesdefines a perimeter and wherein each of the holes is extensible so as toextend the perimeter by at least 20%.
 2. A strainer according to claim1, wherein the resilient deformable material is, or includes, any oneof: an elastomeric polymer, a rubber, synthetic rubber, rubber-likematerial, polychloroprene or nitrile.
 3. A strainer according to claim1, wherein the resilient deformable material has a Young's modulus ofless than a Young's modulus of a metal.
 4. A strainer according to claim1, wherein the resilient deformable material has a Young's modulus ofless than a Young's modulus of a hard plastics material.
 5. A straineraccording to claim 1, wherein a coupling component is disposed adjacentthe outlet and wherein the coupling component is a metal ring.
 6. Astrainer according to claim 5, wherein the metal ring is embedded withinthe material.
 7. A strainer according to claim 1, wherein the straineris formed by injection moulding.
 8. A strainer according to claim 1,wherein the strainer is of a unitary construction.
 9. A straineraccording to claim 1, wherein the material is formed from a combinationof: standard Malaysian rubber; an activator; an accelerator; acrosslinking agent, a processing aid; process oil; a wax; an antioxidantand antiozonant; and semi re-enforcing carbon black.
 10. A straineraccording to claim 9, wherein: the Standard Malaysian Rubber is SMR10;the activator is zinc oxide and/or stearic acid; the accelerator isN-cyclohexyl-2-benzothiazole sulphonamide; the crosslinking agent issulphur; the processing aid is a viscosity reducer; the process oil is aparaffinic oil; the wax is paraffinic wax; the antioxidant andantiozonant is N-(1,3-Dimethylbutyl)-N′-phenyl-p-phenylenediamine and/orN-Isopropyl-N′-phenyl-p-phenylenediamine; and the semi re-enforcingcarbon black is N774.
 11. A strainer according to claim 1, wherein thematerial is formed from a combination of: polychloroprene; a cure systemand crosslinking agent; a processing aid; a flame retardant; an acidacceptor; an antioxidant and antiozonant; and semi re-enforcing carbonblack.
 12. A strainer according to claim 11, wherein: the cure systemand crosslinking agent is zinc oxide and/or Ethylene thiourea and/orTetramethylthiuram disulfid; the processing aid is stearic acid and/oran emulsion plasticizer dispersing and processing additive; the flameretardant is antimony trioxide and/or chlorinated polyethylene and/oralumina trihydrate and/or zinc borate; the acid acceptor is magnesiumoxide; the antioxidant and antiozonant isN-(1,3-Dimethylbutyl)-N′-phenyl-p-phenylenediamine; and the semire-enforcing carbon black is N330.
 13. A strainer according to claim 1,wherein the combined cross sectional area of the plurality of holes isbetween 2 and 6 times the cross sectional area of the outlet.
 14. Astrainer according to claim 1, wherein the combined cross sectional areaof the plurality of holes is between 6 and 14 times the cross sectionalarea of the outlet.
 15. A strainer according to claim 1, wherein thestrainer has a weight of less than 1 kg.
 16. A strainer according toclaim 1, wherein the body is a cylindrical shaft defining a distal endand a proximal end and wherein a tapered head is disposed at the distalend and wherein the outlet is at the proximal end.
 17. A straineraccording to claim 16, wherein the tapered head defines an includedangle of between 40° and 70°.
 18. A strainer according to claim 1,wherein the body is deformable upon the application of the compressiveforce, configured to crush the hollow internal chamber substantiallyflat prior to the body resiliently returning substantially to itspre-deformation shape when the compressive force is no longer applied.19. A method of pumping a liquid including: providing a pump attached toa hose, the hose having a distal end defining an inlet; providing astrainer including: a body defining a plurality of inlet holes, each ofthe inlet holes being in fluid communication with a hollow internalchamber; and an outlet being in fluid communication with the hollowinternal chamber, the outlet being for attachment to the inlet of thehose; wherein the body is formed from a resilient deformable material tobring opposed sides of the internal chamber into contact with each otherin response to the application of a compressive force prior to the bodyresiliently returning substantially to its pre-deformation shape whenthe force is no longer applied and wherein each of the holes defines aperimeter and wherein each of the holes is extensible so as to extendthe perimeter by at least 20%; attaching the outlet of the strainer tothe inlet of the hose; operating the pump to suck the liquid into theplurality of holes, through the hollow chamber, out the outlet, and intothe hose; and periodically detaching the strainer and impacting thestrainer against a solid object to dislodge contaminants clogging theholes.
 20. A method according to claim 19, including periodicallyreversing the flow direction of the pump such that liquid is pumped outof the holes to dislodge contaminants clogging the holes.